Retirement is a major milestone that brings many life changes. One thing that doesn't change for most people: the fear of running out of money. According to the Transamerica Center for Retirement Studies, the most frequently reported retirement worry is outliving savings and investments. Across all ages, 51% of respondents cited this concern, and 41% of retirees claim the same fear. Additionally, only 46% of retirees think they've built a nest egg large enough to last through retirement.